Backlight unit, electro-optical device, and electronic apparatus

ABSTRACT

A backlight unit includes: an arrangement surface on which a plurality of light sources are arranged, and a plurality of reflection surfaces erected from a plurality of edges of the arrangement surface. The light emitted from the light sources and the light reflected from the reflection surfaces irradiate to an irradiation area surrounded by the reflection surfaces which are each inclined at an inclination angle smaller than 90 degrees with respect to the arrangement surface. At least one reflection surface includes a large inclination area inclined at a large inclination angle and a small inclination area inclined at a small inclination angle. The light source arranged close to the large inclination area is disposed closer to the outside frame of the irradiation area than the other light sources arranged close to the small inclination area in plan view from the irradiation area.

BACKGROUND

1. Technical Field

The present invention relates to a backlight unit including a pluralityof light sources, and an electro-optical device and an electronicapparatus using the backlight unit.

2. Related Art

In the related art, a liquid crystal display device (LCD) as anelectro-optical device includes a display panel displaying an image anda backlight unit disposed on the rear surface of the display panel andemitting light toward the display panel.

As the backlight unit, a direct-type backlight unit having a pluralityof light sources arranged directly below the display panel has beenknown (for example, see JP-A-2007-80798).

The direct-type backlight unit disclosed in JP-A-2007-80798 includes abox-like case having a bottom plate, a plurality of light sourcesarranged inside the case, and a display panel disposed so as to cover anopening of the case. The case has the bottom plate and a plurality ofside walls obliquely erected from the edges of the bottom plate. Theplurality of light sources are arranged on the bottom plate in a zigzagshape. In addition, the plurality of side walls are erected at the sameinclination angle.

Light emitted from the plurality of light sources and light reflectedfrom inner surfaces (reflection surfaces) of the plurality of side wallsirradiate to an irradiation area surrounded by the upper ends of theplurality of side walls.

In the backlight unit disclosed in JP-A-2007-80798, however, since theplurality of light sources are arranged in a zigzag shape, the lightsources distant from the side walls and the light sources close to theside walls exist. Therefore, in the light sources distant from the sidewalls, an amount of light reflected from the reflection surfaces of theside walls is reduced. In contrast, in the light sources close to theside walls, an amount of light reflected from the reflection surfaces ofthe side walls is increased. For this reason, a problem may occur inthat an amount of light in the irradiation area becomes non-uniform.Moreover, the amount of light reflected from the reflection surfaces ofthe side walls is reduced in the light sources distant from the sidewalls. Therefore, a problem may occur in that an amount of light emittedto a side of the outside frame of the irradiation area is reduced,thereby deteriorating optical characteristics.

On the other hand, in a liquid crystal display device which is anassembly of the backlight unit and the display panel, when the amount oflight in the irradiation area of the backlight unit is not uniform, aproblem may occur in that display irregularities such as brightnessirregularity and color irregularity occurs in an effective display areawhere an image of the display panel is displayed.

SUMMARY

An advantage of some aspects of the invention is that it provides abacklight unit capable of allowing an amount of light in the entireirradiation area to be uniform to improve optical characteristics,effectively using light from a light source to realize lower powerconsumption, and being used for a bright illuminating device, and anelectro-optical device and an electronic apparatus capable ofsuppressing display irregularities in an effective display area.

According to an aspect of the invention, there is provided a backlightunit including: an arrangement surface on which a plurality of lightsources are arranged; and a plurality of reflection surfaces which areerected from a plurality of edges of the arrangement surface and reflecta light from the plurality of light sources. The light emitted from thelight sources and the light reflected from the plurality of reflectionsurfaces irradiate to an irradiation area surrounded by the plurality ofreflection surfaces. The plurality of reflection surfaces are eachinclined at an inclination angle smaller than 90 degrees with respect toextension surface of the arrangement surface which extends toward theoutside of the reflection surface. At least one reflection surface ofthe plurality of reflection surfaces includes a large inclination areainclined at a large inclination angle and a small inclination areainclined at a small inclination angle. In plan view from the irradiationarea, the light source arranged close to the large inclination area isdisposed closer to the outside frame of the irradiation area than theother light sources arranged close to the small inclination area.

With such a configuration, in the small inclination area, the lightincident from the light sources arranged at the positions distant fromeach other is reflected at the large reflection angle and output to theoutside frame of the irradiation area. Accordingly, the amount of lightoutput to the outside frame of the irradiation area is not reduced. Inaddition, in the large inclination area, the light incident from thelight sources close to the large inclination area is reflected at asmall reflection angle to supplement an area where the amount of lightin the irradiation area is reduced. Accordingly, since the amount oflight in the entire irradiation area is uniform, the bright backlightunit improved in optical characteristics to realize low powerconsumption can be provided.

According to another aspect of the invention, there is provided abacklight unit including: an arrangement surface on which a plurality oflight sources are arranged; and a plurality of reflection surfaces whichare erected from a plurality of edges of the arrangement surface andreflect a light from the plurality of light sources. The light emittedfrom the light sources and the light reflected from the plurality ofreflection surfaces irradiate to an irradiation area surrounded by theplurality of reflection surfaces. The plurality of reflection surfacesare each inclined at an inclination angle smaller than 90 degrees withrespect to extension surface of the arrangement surface which extendstoward the outside of the reflection surface. At least one reflectionsurface of the plurality of reflection surfaces includes a largeinclination area inclined at a large inclination angle and a smallinclination area inclined at a small inclination angle. The largeinclination area is provided at a position to which a larger amount oflight is emitted from the light sources and the small inclination areais provided at a position to which a smaller amount of light is emittedfrom the light sources.

With such a configuration, since the light from the large inclinationarea supplements the area where the amount of light in the irradiationarea is reduced and the light from the small inclination area is outputto the outside frame of the irradiation area, the amount of light outputto the outside frame of the irradiation area is not reduced.Accordingly, since the amount of light in the entire irradiation area isuniform, the bright backlight unit improved in optical characteristicsto realize low power consumption can be provided.

In the backlight unit according to this aspect of the invention, thereflection surface may be formed in a surface which continuouslyconnects the large inclination area and the small inclination area.

The backlight unit according to the above aspect of the invention mayfurther include a case which includes a bottom plate and a plurality ofside walls erected from edges of the bottom plate. The arrangementsurface on which the plurality of light sources are arranged is placedon an inner surface of the bottom plate. The plurality of reflectionsurfaces from which the light emitted from the plurality of lightsources is reflected are arranged on inner surfaces of the plurality ofside walls.

The backlight unit according to the above aspect of the invention mayfurther include a case which includes a bottom plate and a plurality ofside walls erected from edges of the bottom plate. The bottom plate isthe arrangement surface on which the plurality of light sources arearranged. The plurality of reflection surfaces on which the lightemitted from the plurality of light sources is reflected are arranged oninner surfaces of the plurality of side walls.

In the backlight unit according to this aspect of the invention, a spacemay be formed between the outside of the small inclination area and theinside of the side wall.

With such a configuration, the large space is present between theoutside of the small inclination area and the inside of the side wall.Accordingly, it is possible to make effective use of the space.

In the backlight unit according to this aspect of the invention, anelectronic component may be provided in the space.

With such a configuration, the size of the backlight unit can bedesigned to be reduced.

In the backlight unit according to this aspect of the invention, adirection of the peak of the amount of light emitted from the lightsources may be inclined at an angle from 50 degrees to 80 degrees withrespect to a front direction of the light sources. With such aconfiguration, the light is effectively reflected toward the irradiationarea from the plurality of reflection surfaces in that the direction ofthe peak of the amount of light emitted from the light sources isinclined at the angle from 50 degrees to 80 degrees with respect to thefront direction of the light sources. Accordingly, the backlight unitfurther improved in the optical characteristics can be provided.

According to still another aspect of the invention, there is provided anelectro-optical device including the backlight unit having theabove-described configuration and a display panel which is disposed tooverlap with the irradiation area of the backlight unit. The displaypanel includes an effective display area for displaying an image. Inplan view from the irradiation area, an outside frame of the effectivedisplay area overlaps with the plurality of reflection surfaces of thebacklight unit. Moreover, the effective display area may be providedwithin the irradiation area.

With such a configuration, a uniform amount of light emitted toward theirradiation area of the backlight unit is surely output to the outsideframe of the effective display area of the display panel. Accordingly,by suppressing the display irregularities in the effective display area,an image having high quality and high brightness can be displayed.

According to still another aspect of the invention, there is provided anelectronic apparatus comprising the electro-optical device having theabove-described configuration. With such a configuration, it is possibleto provide the electronic apparatus including a display device capableof displaying an image having high quality and high brightness.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a top view illustrating a backlight unit according to a firstembodiment of the invention.

FIG. 2 is a sectional view taken along the line II-II of FIG. 1.

FIG. 3 is a sectional view taken along the line III-III of FIG. 1.

FIGS. 4A and 4B are enlarged views illustrating major units of FIGS. 2and 3, respectively.

FIG. 5 is a sectional view illustrating a backlight unit according to asecond embodiment of the invention.

FIG. 6 is a top view illustrating an electro-optical device according toa third embodiment of the invention.

FIG. 7 is a sectional view taken along the line VII-VII of FIG. 6.

FIG. 8 is a perspective view illustrating an electronic apparatusaccording to a fourth embodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, preferred embodiments (hereinafter, also referred to asembodiments) of the invention will be described in detail with referenceto the drawings.

First Embodiment: Backlight Unit

FIG. 1 is a top view illustrating a backlight unit according to theinvention. FIG. 2 is a sectional view taken along the line II-II ofFIG. 1. FIG. 3 is a sectional view taken along the line III-III ofFIG. 1. FIG. 4A is an enlarged view illustrating major units of FIG. 2.FIG. 4B is an enlarged view illustrating major units of FIG. 3.

A backlight unit 10 according to this embodiment includes a box-likecase 1 having a bottom plate and a plurality of light sources 2 a to 2 earranged in a predetermined arrangement manner inside the case 1.

The case 1 includes a bottom plate 1 a and a plurality of side walls 1 bto 1 e erected from the edges of the bottom plate 1 a. An arrangementplate 3 is placed on the bottom plate 1 a. In addition, a plurality oflight sources 2 are arranged on an arrangement surface 3 a of thearrangement plate 3 and inclination walls 4 to 7 are arranged betweenthe edges of the arrangement plate 3 and the upper edges of the sidewalls 1 b to 1 e.

Light sources 2 a to 2 d among the plurality of light sources 2 a to 2 eare arranged in the vicinity of four corners of the arrangement surface3 a and the remaining light source 2 e is arranged at the center (thecenter of the arrangement surface 3 a) of an area binding the lightsources 2 a to 2 d.

The light sources 2 a to 2 e are members which each include alight-emitting element such as an LED (Light-Emitting Diode) and anoptical member such as a convex lens which is disposed at a light outputposition of the light-emitting element and formed of a material such asresin. The optical member is capable of outputting more light emittedfrom the light-emitting element in a direction intersecting a frontdirection than in the front direction. The plurality of light sources 2a to 2 e according to this embodiment is a light source which emitslight so that a direction of the peak of the amount of light emitted isinclined at an angle from 50 degrees to 80 degrees with respect to thefront direction of the light source.

Inner surfaces 4 a to 7 a of the inclination walls 4 to 7 are eachconfigured as an inclination surface which is inclined at an inclinationangle smaller than 90 degrees with respect to an extension surface ofthe arrangement surface 3 a extends toward the outside of the innersurfaces. The inner surfaces 4 a to 7 a are reflection surfaces(hereinafter, referred to as reflection surfaces 4 a to 7 a) from whichlight emitted from the light sources 2 a to 2 e is reflected. Inaddition, light emitted from the plurality of light sources 2 a to 2 eand light emitted from the reflection surfaces 4 a to 7 a irradiatetoward an opening surrounded by the reflection surfaces 4 a to 7 a.

The reflection surface 7 a of the side wall 7 is a surface whichcontinuously connects a small inclination area 7 a 1 inclined at a smallinclination angle and large inclination areas 7 a 2 inclined at a largeinclination angle.

That is, the small inclination area 7 a 1 inclined at the smallinclination angle is formed at a position distant from the light source2 e in the middle portion in a longitudinal direction of the reflectionsurface 7 a (see FIG. 2). The large inclination areas 7 a 2 inclined atthe large inclination angle are formed at positions which are on bothends in the longitudinal direction of the reflection surface 7 a andclose to the light sources 2 a and 2 d so that the inclination anglethereof is gradually changed toward the both ends in the longitudinaldirection from the small inclination area 7 a 1 (see FIG. 3).

The reflection surface 5 a of the side wall 5 is also a surface in whicha small inclination area 5 a 1 inclined at a small inclination angle isformed at a position distant from the light source 2 e in the middleportion in a longitudinal direction of the reflection surface 5 a (seeFIG. 2) and large inclination areas 5 a 2 inclined at a largeinclination angle are formed at positions which are in both ends in thelongitudinal direction of the reflection surface 5 a and close to thelight sources 2 b and 2 c so that the inclination angle thereof isgradually changed toward the both ends in the longitudinal direction(see FIG. 3).

The reflection surface 4 a of the side wall 4 is also a surface in whicha small inclination area 4 a 1 inclined at a small inclination angle isformed at a position distant from the light source 2 e in the middleportion in a longitudinal direction of the reflection surface 4 a andlarge inclination areas 4 a 2 inclined at a large inclination angle areformed at positions which are in both ends in the longitudinal directionof the reflection surface 4 a and close to the light sources 2 a and 2 bso that the inclination angle thereof is gradually changed toward theboth ends in the longitudinal direction. Moreover, The reflectionsurface 6 a of the side wall 6 is also a surface in which a smallinclination area 6 a 1 inclined at a small inclination angle is formedat a position distant from the light source 2 e in the middle portion ina longitudinal direction of the reflection surface 6 a and largeinclination areas 6 a 2 inclined at a large inclination angle is formedat positions which are in both ends in the longitudinal direction of thereflection surface 6 a and close to the light sources 2 c and 2 d sothat the inclination angle thereof is gradually changed toward the bothends in the longitudinal direction.

That is, in all the side walls, the small inclination area and the largeinclination areas are connected as a continuous surface.

As shown in FIG. 2, the case 1 is provided with large spatial portionson sides of the rear surfaces of the small inclination areas 7 a 1 and 5a 1 inclined at the small inclination angle. In the spatial portions,spaces 8 and 9 capable of accommodating an electronic component such asa control unit controlling the light sources 2 of the backlight unit 10are formed. Even though not illustrated, large spatial portions areprovided on sides of the rear surfaces of the small inclination areas 4a 1 and 6 a 1 inclined at the small inclination angle. In the spatialportions, spaces capable of accommodating an electronic component areformed.

When the plurality of light sources 2 a to 2 e of the backlight unit 10according to this embodiment emit light, the light emitted from theplurality of light sources 2 a to 2 e and light emitted from the lightsources 2 a to 2 e and reflected from the reflection surfaces 4 a to 7 aare incident on the opening surrounded by the outer ends of thereflection surfaces 4 a to 7 a, that is, are incident on a irradiationarea Ar having a large area shown in FIG. 1.

In this embodiment, as shown in FIG. 4A, the small inclination area 5 a1 inclined at the small inclination angle is formed at the positiondistant from the light sources 2 e disposed in the middle portion of thearrangement surface 3 a. With such a configuration, since in the smallinclination area 5 a 1, the light incident from the light source 2 e isreflected at a large inclination angle α and output to the outside frameof the irradiation area Ar, an amount of light output to the outsideframe of the irradiation area Ar is not reduced. Likewise, the smallinclination areas 4 a 1, 6 a 1, and 7 a 1 are also formed at thepositions distant from the light source 2 e disposed in the middleportion of the arrangement surface 3 a.

As shown in FIG. 4B, the large inclination area 5 a 2 inclined at thelarge inclination area is formed at a position close to the light source2 c disposed in the corner of the arrangement surface 3 a. Likewise, thelarge inclination areas 4 a 2, 6 a 2, and 7 a 2 are also formed atpositions close to the light sources 2 a, 2 b, and 2 d disposed in thecorners of the arrangement surface 3 a, respectively.

In this way, the light sources 2 a to 2 d disposed close to the largeinclination areas 4 a 2, 5 a 2, 6 a 2, and 7 a 2 are arranged closer tothe outside frame of the irradiation area Ar than the light source 2 edisposed close to the small inclination areas 4 a 1, 5 a 1, 6 a 1, and 7a 1 in plan view from the irradiation area Ar. With such aconfiguration, since in the small inclination areas 4 a 1, 5 a 1, 6 a 1,and 7 a 1, the light incident from the light source 2 e is reflected atthe large inclination angle α and output to the outside frame of theirradiation area Ar, the amount of light output to the outside frame ofthe irradiation area Ar is not reduced. Moreover, by reflecting thelight incident from the light sources 2 a to 2 d at a small reflectionangle β in the large inclination areas 4 a 2, 5 a 2, 6 a 2, and 7 a 2,an area where the amount of light in the irradiation area Ar is reducedis supplemented.

Even when the light source 2 e is disposed at the position distant fromthe reflection surfaces 4 a to 7 a and the light sources 2 a to 2 d aredisposed close to the reflection surfaces 4 a to 7 a in the arrangementsurface 3 a of the case 1, the amount of light output toward the outsideframe of the irradiation area Ar is not reduced and the amount of lightis uniform in the entire irradiation area Ar. Accordingly, the backlightunit 10 improved in optical characteristics can be provided.

The light sources 2 a to 2 e according to this embodiment emit lightsuch that the direction of the peak of the amount of light emitted isinclined at the angle from 50 degrees to 80 degrees with respect to thefront direction of the light sources. With such a configuration, sincethe light emitted from the light sources 2 a to 2 e is effectivelyreflected toward the irradiation area Ar from the reflection surfaces 4a to 7 a and output to the outside frame of the irradiation area Ar,brightness in the outside frame of the irradiation area Ar is improved.Accordingly, the backlight unit 10 further improved in opticalcharacteristics can be provided.

In the backlight unit 10 according to this embodiment, it is possible tomake effective use of the spaces 8 and 9 by accommodating electroniccomponents in the spaces 8 and 9 formed in the rear surfaces of thesmall inclination areas 4 a 1, 5 a 1, 6 a 1, and 7 a 1.

In this embodiment, the five light sources 2 a to 2 e are disposed, butdoes not limit the gist of the invention. The same advantages can beobtained by arranging several light sources in a zigzag shape andallowing the light sources arranged close to the large inclination areasto be disposed closer to the outside frame of the irradiation area thanthe light sources arranged close to the small inclination areas in planview from the irradiation area Ar.

Second Embodiment: Backlight Unit

FIG. 5 is a sectional view illustrating a backlight unit according to asecond embodiment of the invention.

In a backlight unit 10 according to this embodiment, the arrangementplate 3 is not placed on a bottom plate 1 a of a case 1 and a pluralityof light sources 2 a to 2 e are arranged on the upper surface of thebottom plate 1 a.

The shape of the respective reflection surfaces 4 a to 7 a is the sameas that according to the first embodiment. In plan view from theirradiation area Ar, the light sources 2 a to 2 d arranged close to thelarge inclination areas 4 a 2, 5 a 2, 6 a 2, and 7 a 2 are disposedcloser to the outside frame of the irradiation area Ar than the lightsource 2 e arranged close to the small inclination areas 4 a 1, 5 a 1, 6a 1, and 7 a 1.

The arrangement surface of the invention corresponds to the uppersurface of the bottom plate 1 a.

According to this embodiment, the same advantages of the firstembodiment can be obtained. Moreover, since the arrangement plate 3 isnot placed on the bottom plate 1 a of the case 1, the number ofconstituent elements can be reduced.

Third Embodiment: Liquid Crystal Display Device

Next, a liquid crystal display device as an electro-optical device ofthe invention using the backlight unit 10 having the above-describedconfiguration will be described.

FIG. 6 is a top view illustrating the liquid crystal display device.FIG. 7 is a sectional view taken along the line VII-VII of FIG. 6.

According to this embodiment, a liquid crystal display device 20includes a liquid crystal display panel 11, a diffusion plate 12, anoptical sheet 13, and a liquid crystal driving IC (not shown) formed onthe backlight unit 10 according to the first embodiment.

The liquid crystal display panel 11 includes a front surface substrate11 b and a rear surface substrate 11 c opposed to each other with aliquid crystal layer 11 a interposed therebetween, and also includes aseal material 11 d formed in a frame shape between the circumference ofthe two substrates to adhere the two substrates. The front surfacesubstrate 11 b has a configuration in which a liquid crystal alignmentcontrol layer having a front surface electrode made of a transparentconductive material, an alignment film, or the like is formed on asurface close to the liquid crystal layer of a substrate body as atransparent substrate. The rear surface substrate 11 c also has aconfiguration in which a liquid crystal alignment control layer having arear surface electrode made of a transparent conductive material, analignment film, or the like is formed on a surface close to the liquidcrystal layer of a substrate body as a transparent substrate. Inaddition, a protrusion portion is provided in one of the front surfacesubstrate 11 b and the rear surface substrate 11 c so as to protrudetoward the outer circumference of the other thereof. A wiring pattern isformed on the protrusion portion. The front surface electrode of thefront surface substrate 11 b and the rear surface electrode of the rearsurface substrate 11 c are electrically connected to the wiring patternformed on the protrusion portion. In addition, the liquid crystaldriving IC electrically driving the liquid crystal display panel 11 ismounted on the wiring pattern formed on the protrusion portion.

The diffusion plate 12, the optical sheet 13, and the liquid crystaldisplay panel 11 are laminated on the backlight unit 10.

The liquid crystal display panel 11 is provided with an effectivedisplay area Ai which is an area for displaying an image.

In plan view of the liquid crystal display device 20, the outside frameof the effective display area Ai of the liquid crystal display panel 11overlaps with the reflection surfaces 4 a to 7 a of the backlight unit10. The effective display area Ai of the liquid crystal display panel 11is formed within the irradiation area Ar of the backlight unit 10.

A display panel according to the invention corresponds to the liquidcrystal display panel 11.

In the liquid crystal display device 20 according to this embodiment,the outside frame of the effective display area Ai of the liquid crystaldisplay panel 11 overlaps with the reflection surfaces 4 a to 7 a of thebacklight unit 10 in plan view. In addition, the light emitted from theplurality of light sources 2 a to 2 e of the backlight unit 10 andreflected from the reflection surfaces 4 a to 7 a surely irradiates tothe outside frame of the effective display area Ai. Therefore, it ispossible to prevent the occurrence of display irregularities, such asbrightness irregularity and color irregularity, in the effective displayarea Ai.

According to this embodiment, since the effective display area Ai of theliquid crystal display panel 11 is provided within the irradiation areaAr of the backlight unit 10 in plan view of the liquid crystal displaydevice 20, an amount of light emitted to the outside frame of theeffective display area Ai is not reduced and the amount of light in theentire effective display area Ai is uniform. Accordingly, an imagehaving high quality and high brightness can be displayed in theeffective display area Ai.

Fourth Embodiment: Personal Computer

Next, a personal computer as an electronic apparatus according to theinvention using the liquid crystal display device 20 having the aboveconfiguration will be described.

a personal computer 30 shown in FIG. 8 includes a main body 32 having akeyboard 31 and a display device 33 to which the liquid crystal displaydevice 20 is applied.

In the personal computer 30 according to this embodiment, the displaydevice 33 displaying an image having high equality and high brightnesscan be provided.

The electronic apparatus according to the invention is not limited tothe personal computer 30, but the invention is applicable to variouselectronic apparatuses. For example, the invention is applicable to aPDA (personal digital assistant), a small information electronicapparatus such as a palmtop computer, a mobile phone, an electronicbook, a digital still camera, a liquid crystal television, a view findertype or monitor direct view type videotape recorder, a pager, anelectronic organizer, an electronic calculator, a word processor, aworkstation, a video phone, a POS terminal, a printing apparatus, andthe like.

The entire disclosure of Japanese Patent Application No. 2008-199330,filed Aug. 1, 2008 is expressly incorporated by reference herein.

1. A backlight unit comprising: an arrangement surface on which aplurality of light sources are arranged; and a plurality of reflectionsurfaces which are erected from a plurality of edges of the arrangementsurface and reflect a light from the plurality of light sources, whereinthe light emitted from the light sources and the light reflected fromthe plurality of reflection surfaces irradiate to an irradiation areasurrounded by the plurality of reflection surfaces; the plurality ofreflection surfaces are each inclined at an inclination angle smallerthan 90 degrees with respect to extension surface of the arrangementsurface which extends toward the outside of the reflection surface; atleast one reflection surface of the plurality of reflection surfacesincludes a large inclination area inclined at a large inclination angleand a small inclination area inclined at a small inclination angle; andthe light source arranged close to the large inclination area isdisposed closer to the outside frame of the irradiation area than theother light sources arranged close to the small inclination area in planview from the irradiation area.
 2. A backlight unit comprising: anarrangement surface on which a plurality of light sources are arranged;and a plurality of reflection surfaces which are erected from aplurality of edges of the arrangement surface and reflect a light fromthe plurality of light sources, wherein the light emitted from the lightsources and the light reflected from the plurality of reflectionsurfaces irradiate to an irradiation area surrounded by the plurality ofreflection surfaces; the plurality of reflection surfaces are eachinclined at an inclination angle smaller than 90 degrees with respect toextension surface of the arrangement surface which extends toward theoutside of the reflection surface; at least one reflection surface ofthe plurality of reflection surfaces includes a large inclination areainclined at a large inclination angle and a small inclination areainclined at a small inclination angle; and the large inclination area isprovided at a position to which a larger amount of light is emitted fromthe light sources and the small inclination area is provided at aposition to which a smaller amount of light is emitted from the lightsources.
 3. The backlight unit according to claim 1, wherein thereflection surface is formed in a surface which continuously connectsthe large inclination area and the small inclination area.
 4. Thebacklight unit according to claim 1, further comprising: a case whichincludes a bottom plate and a plurality of side walls erected from edgesof the bottom plate, wherein the arrangement surface on which theplurality of light sources are arranged is placed on an inner surface ofthe bottom plate, and wherein the plurality of reflection surfaces fromwhich the light emitted from the plurality of light sources is reflectedare arranged on inner surfaces of the plurality of side walls.
 5. Thebacklight unit according to claim 1, further comprising: a case whichincludes a bottom plate and a plurality of side walls erected from edgesof the bottom plate, wherein the bottom plate is the arrangement surfaceon which the plurality of light sources are arranged, and wherein theplurality of reflection surfaces on which the light emitted from theplurality of light sources is reflected are arranged on inner surfacesof the plurality of side walls.
 6. The backlight unit according to claim4, wherein a space is formed between the outside of the smallinclination area and the inside of the side wall.
 7. The backlight unitaccording to claim 6, wherein an electronic component is provided in thespace.
 8. The backlight unit according to claim 1, wherein a directionof the peak of the amount of light emitted from the light sources isinclined at an angle from 50 degrees to 80 degrees with respect to afront direction of the light sources.
 9. An electro-optical devicecomprising: the backlight unit according to claim 1; and a display panelwhich is disposed to overlap with the irradiation area of the backlightunit, wherein the display panel includes an effective display area fordisplaying an image, and wherein in plan view from the irradiation area,an outside frame of the effective display area overlaps with theplurality of reflection area of the backlight unit.
 10. Theelectro-optical device according to claim 9, wherein the effectivedisplay area is provided within the irradiation area.
 11. An electronicapparatus comprising the electro-optical device according to claim 9.